Kier and Downer have agreed terms for the disposal of KHSA for a cash consideration of up to £24m ($43.7m).
Acquired by Kier through the takeover of Mouchel Group in June 2015, KHSA has been providing road asset management and maintenance services in Australia as part of a joint venture with Downer.
Gross assets for KHSA stood at £52.1m on 30 June this year, with pre-tax profit of £7m.
The disposal, to be completed in early 2019, is expected to generate about £15m in profit, which Kier plans to use to reduce its net debt.
Meanwhile, Kier said in a trading update that it anticipates average monthly net debt of about £390m for the first half of the 2019 financial year, down from the £410m for the second half of 2018.